Although everyone would agree that most of the speech we hear originates in a human vocal tract, it is less widely accepted that the cognitive activities involved in speech production and speech perception are intrically linked. Many theorists hold th view that speech is analyzed by the ear and brain in a purely acoustic manner without reference to the characteristics of the vocal tract. Other theorists think that the unit of speech perception is the gesture, or the coordinated activity of a set of articulators, such as the jaw and lips, achieving a phonetic goal such as lip closure. The concept of a gesture as a perceptual unit has led to new insights into many speech production phenomena, and specific models have been developed from which testable predictions have recently emerged. The proposed experiments will seek further results to substantiate the claim that speech production and perception are related and to validate the articulatory gesture as the link between the two. This theoretical perspective has been fruitfully applied to problems in language acquisition, language change, and certain language disabilities. Advances stemming from th proposed research are expected to lead to even broader applications. The method of inquiry we propose to use is to show that those acoustic parameters that vary together as a result of some articulatory movement also cohere in perception. This will be accomplished by obtaining measurements of the speech articulators in action via magnetometry, applying those data to the control of an articulatory model, and then evaluating he synthetic speech output based on a variety of listener responses. Thus, we will be able to test the link between the production and the perception of these speech sounds in a more direct way than has been possible before. Rather than inferring the perceptual effects from measured movements, we will manipulate the movements to see what is critical. And, rather than modify the acoustics and trust that the underlying speech gestures are physiologically attainable, we can base our perceptual stimuli on realistic movements. We expect the results of these experiments to reveal more clearly than ever before the nature and strength of the link between production and perception of speech.